The present invention generally relates to the continuous separation of solid particles, such as soot, from a fluid, such as oil, by use of a centrifuge. More specifically, but not exclusively, the present invention relates to a centrifuge housing and base design to permit the controlled introduction of air in order to assist with drainage of the fluid from the centrifuge.
Diesel engines are designed with relatively sophisticated air and fuel filters (cleaners) in an effort to keep dirt and debris out of the engine. Even with these air and fuel cleaners, dirt and debris, including engine-generated wear debris, will find a way into the lubricating oil of the.engine. The result is wear on critical engine components and if this condition is left unsolved or not remedied, engine failure. For this reason, many engines are designed with full flow oil filters that continually clean the oil as it circulates between the lubricant sump and engine parts.
There are a number of design constraints and considerations for such full flow filters and typically these constraints mean that such filters can only remove those dirt particles that are -in the range of 10 microns or larger. While removal of particles of this size may prevent a catastrophic failure, harmful wear will still be caused by smaller particles of dirt that get into and remain in the oil. In order to try to address the concern over small particles, designers have gone to bypass filtering systems which filter a predefined percentage of the total oil flow. Since bypass filters may be able to trap particles less than approximately 10 microns, the combination of a full flow filter and bypass filter offers substantial improvement over the use of only a full flow filter.
One of the realities of centrifuge designs of the type generally described (above) is that the oil drains by the action (force) of gravity. This in turn has an effect on where the centrifuge should be positioned within the engine relative to the location of the oil sump. It is important to position the centrifuge, specifically the centrifuge housing, above the sump so that sufficient head pressure is created to adequately drain the oil from the centrifuge housing. Not only should the volume and completeness of the oil drainage be a factor, but the rate of oil drainage is also important. The concept of xe2x80x9cadequatexe2x80x9d draining in the context of this invention is that amount or degree or rate of drainage which keeps the oil from backing up to the point that it floods the centrifuge. Flooding the centrifuge effectively negates any beneficial utilization of the centrifuge for separating particulate matter from the oil flowing through the centrifuge.
The requirement to position the centrifuge housing above the sump limits the number of available mounting locations. The need to position the centrifuge housing high enough above the sump to create a sufficient head pressure further limits the number of available mounting locations. As the number of available mounting locations decreases, the number of potential customers that can use this type of centrifuge also decreases. The present invention contemplates and discloses, the use of air pressure to assist with the oil draining from the centrifuge housing, thereby allowing the centrifuge housing to have a greater choice of mounting locations. This in turn increases the number of potential customers for use of this type of centrifuge.
A related design disadvantage of gravity-drain centrifuge housings is the need to use larger diameter hoses coming from the centrifuge drain and going into the sump. The maximum drain flow volume is a function of the minimum cross sectional area of the drain opening and the connecting hose or conduit. It is normal to select a connecting hose size to match the drain outlet in the housing. The need for a large diameter hose is due to the fact that the oil going into the sump needs to vent in order for the oil to reach the sump. Without a large diameter hose, the oil backs up and floods the centrifuge casting.
The present invention provides a novel and unobvious design for an air-assisted drain for a centrifuge housing which uses a pressure cutoff valve. In this way, air is only introduced into the centrifuge housing when the centrifuge is operating and oil is flowing. The same piston arrangement which governs oil inlet flow into the centrifuge rotor also governs and controls the flow of air (under pressure) into the centrifuge housing in order to help push out the oil after processing to separate out particulate matter.
A centrifuge assembly for processing a fluid according to one embodiment of the present invention is constructed and arranged with air-assisted drainage of the fluid. The centrifuge assembly includes a centrifuge having a centrifuge housing which defines a hollow interior and a fluid processing device, such as a centrifuge rotor, which is positioned in the centrifuge housing interior for centrifugal separation of particulate matter from the fluid. The centrifuge assembly further includes a housing base which defines a fluid-in conduit in flow communication with the centrifuge, a fluid-out drain conduit in flow communication with the centrifuge, an air-in passageway, and an air-out passageway in flow communication with the centrifuge for introducing air into the hollow interior. The centrifuge assembly further includes a flow control piston which is assembled into the housing base and includes a movable piston having a normally-closed position in which the piston blocks the flow of fluid into the centrifuge rotor and blocks the flow of air into the centrifuge housing. The piston is movable to an open position in response to fluid pressure in the fluid-in conduit. With the piston in its open position, fluid is able to flow into the centrifuge rotor and air is able to flow into the centrifuge housing for applying air pressure on the fluid in the centrifuge rotor in order to assist in the drainage of this fluid by way of the fluid-out drain conduit.
One object of the present invention is to provide an improved centrifuge assembly with air-assisted drainage.
Related objects and advantages of the present invention will be apparent from the following description.